The main research goal of the project was to evaluate the velocity model CVM-S4.26, which integrates the perturbations obtained from a 3D tomographic inversion based on the original model CVM-S4. We accomplished this goal by testing the different integration schemes used to build CVM-S4.26 and quantifying the level of improvement (or lack thereof) in the prediction of the ground motion of past 29 earthquakes with low and moderate magnitues (3.6 < M < 5.4). The improvement was measured primarily using a goodness-of-fit criterion that evaluates the match between synthetics and data with a suite of parameters that goes beyond the misfit rule used for the inversion. Our results indicate that CVM-S4.26 (Option 1) is the best of the alternatives and that overall the new model is better than the original model CVM-S4, even for frequencies above 0.2 Hz.

Intellectual Merit

This research provides valuable insight about the robustness of the improvements obtained from 3D tomographic inversions when integrated within models at finer resolutions than that corresponding to the inversion. This gives SCEC scientists the necessary confidence to use the new model CVM-S4.26 in simulations planned for SCEC’s CyberShake and High-F projects.

Broader Impacts

This project provided direct funds and research opportunities for three students at the University of Memphis. In particular, financial support was used for Civil Engineering Ph.D.~student Shima Azizzadeh-Roodpish and Geophysics Ph.D.~student Naeem Khoshnevis. Both these students are affiliated with the Center for Earthquake Research and Information and work under the supervision of the PI. The project also provided an opportunity in undergraduate research for Computer Science B.S.~student Daniel Ault, who received financial support through the MemphiSTEM program to work as a developer for the simulation team. Initial results from the project were presented at the 10th Joint Meeting of the UJNR Panel on Earthquake Research in Sendai, Japan, 14--16 October 2014. Students Azizzadeh-Roodpish and Khoshnevis attended the 2014 SCEC Annual Meeting to disseminate their work. Details are given in the Presentations section below.